The invention relates to a centrifugal pump with a floating ring seal in a sealing chamber for delivered fluid for a pump shaft and web-like flat portions arranged in the sealing chamber between the outside wall thereof and the floating ring seal and extending in longitudinal section substantially parallel to the pump shaft, wherein arranged in the head region of the sealing chamber is at least one closable vent opening.
A centrifugal pump of that kind is described by way of example in a prospectus of April 1986 from the present applicants relating to the so-called NTT series by means of a sectional view for single-stage models; therein the flat portions are radially formed at the transition of a side surface into the peripheral wall of the sealing chamber. It is intended to permit calming and stabilising of the fluid which is passed around the pump shaft.
EP 0 327 549 B1 shows an annular wall which surrounds the floating ring seal or the pump shaft at a spacing and which has radial ribs projecting therefrom, the ribs extending close to the peripheral wall of the sealing chamber. It is also indicated that radial ribs can be directed from the peripheral wall towards the pump shaft.
In consideration of that state of the art the inventor set himself the aim of improving the means for rotational calming and for gas removal and in so doing simplifying manufacture of such centrifugal pumps.
That object is attained by the teaching set forth in the independent claim; the appendant claims set forth advantageous developments. The scope of the invention also embraces all combinations of at least two of the features disclosed in the description, the drawing and/or the claims.
In accordance with the invention a respective blade-like flat portion extends at the peripheral or outside wall of the sealing chamber on each side of the vent opening; those two flat portionsxe2x80x94which are inclined relative to each other in terms of cross-sectionxe2x80x94delimit between them at a spacing relative to the peripheral wall an antechamber of the vent bore with a gap which is approximately parallel to the pump shaft. Fluid passes therethrough radially into the above-mentioned antechamber in which it spends a residence time in a calmed condition.
It has proven to be desirable for the flat portionsxe2x80x94preferably formed from metal materialxe2x80x94to be fixed to the outside or peripheral wall or one of the end or radial walls of the sealing chamber, preferably to the radial wall remote from the intake side; in accordance with a further feature of the invention they then project therefrom at a spacing relative to the peripheral or outside wallxe2x80x94forming a gap. In addition their substantially radial free blade edge is also to define with the other radial wall a radial gap.
The ridge gap at the peripheral wall makes it possible for a head chamber to be formed in the antechamber near the ridge, above the level of fluid, extending at both sides beyond the blade-like antechamber boundaries.
It is also preferred for the two flat portions which define the antechamber for the vent opening, which in cross-section reduces or tapers towards the pump shaft, to form with each other a cross-sectional angle which measures between 70xc2x0 and 90xc2x0 but preferably about 80xc2x0.
In accordance with another feature of the invention moreover a plane which prolongs the flat portion, with the diametral straight line which crosses the center line of the vent opening at a right anglexe2x80x94for a radius of the peripheral wall of about 65 mmxe2x80x94produces an angle of between about 30xc2x0 and 60xc2x0 but preferably about 50xc2x0. It has also proven advantageous for the flat portions to be arranged in such a way that a plane prolonging them delimits an angle of between 30xc2x0 and 60xc2x0, preferably about 50xc2x0, with the diametral straight line crossing the center line of the vent opening at a right angle. That diametral straight line is determined by a radius of the peripheral wall of about 65 mm. Those stipulations favor the cross-sectional shape of the antechamber.
In accordance with the invention the cross-sectional lengths of the two flat portions are different and can be in a ratio to each other as between 3:2 and 3:2.5. In that respect the width of the above-mentioned intake gap should approximately correspond to a sixth of the cross-sectional height of the longer flat portion.
Another aspect of significance is that the flat portion of longer cross-section is arranged ahead of the flat portion of shorter cross-section, in the direction of rotation of the pump shaft, and thereby its base edge can serve as a detachment edge; the flat portion of longer cross-section should extend into a plane which prolongs the cross-section of the other flat portion.
It is also in accordance with the invention for the cross-section of the above-mentioned antechamber to be comparatively small in relation to the cross-section of the sealing chamber, the two preferably being in a ratio of ten to one; the latter gives particularly advantageous results. Even at relatively high pump shaft speeds, the space which occurs above the fluid accommodates the air without any problem.